Neuroscience-Chapter 11 Flashcards
How many orders of magnitude are there in darkest light (luminescence) we can see and the lightest light we can see?
Fourteen
What are the two parallel systems that the visual system is made up of?
Rods and Cones
Where are photoreceptors (rods and cones)?
On the back of the retina
What is the rod system specialized for?
Very low spacial resolution but extremely sensitive to light. Specialized for sensitivity at the expense of resolution
What is the cone system specialized for?
Very high spacial resolution at the expense of sensitivity to light. Specialized for acuity and allows color vision.
Are rods are cones larger?
Rods
What is scotopic vision?
Rod-mediated perception. Happens at the lowest levels of illumination.
What is mesopic vision?
Rod and cone-mediated perception. Happens at levels of illumination around twilight.
What is photopic vision?
Cone-mediated perception
“Seeing” is motivated by which system?
Cones
Are rods or cones more densely packed in the fovea?
Cones
Why is acuity markedly reduced?
Because cones have one cone to one ganglion, whereas rods have more rods to one ganglion (more spacial convergence.
As light hits a photoreceptor, does hyperpolarization or depolarization occur?
Hyperpolarization
How does the cell become hyperpolarized?
Absorption of light by the photoreceptor reduces the concentration of cGMP in the outer segment, leading to closure of cGMP-gated channels and consequently, in the reduction in the inward flow of Na and Ca. K flows out of the cell more rapidly than Na and Ca can flow in, hyperpolarizing the cell.
What happens to the 11-cis isomer when a photon of light hits it?
Its configuration turns to an all-trans retinal.
